The present invention is directed to snowboard boots and, more particularly, to snowboard boots which bend to accommodate different riding positions.
Snowboards differ from skis, which are used in pairs, in that only a single board is used. The rider rides on the snowboard facing sideways so that the direction of snowboard travel and the lengthwise direction of the rider are approximately perpendicular. Both rigidity and flexibility are required of snowboard boots. Rigidity is required so that the foot is held firmly by the snowboard boot, and flexibility is required so that the ankle can tilt with respect to the sole.
Some snowboard boots are designed so that the upper and lower regions, particularly the heel section and the cylindrical section or leg section positioned above the heel section, are capable of relative rotation around the approximate centerline of the snowboard boot (the term xe2x80x9capproximatexe2x80x9d is used because obviously there is not complete lateral symmetry between the left and right boots). Such boots are disclosed in German Patent Publication DE 3,622,746, Japanese Laid-Open Patent Application 7-298092, and elsewhere. In the boots disclosed in these publications, a pivot is used as the swivel design between the heel section and the leg section. The axis of rotation of this pivot lies approximately on the vertical plane which contains the longitudinal line of the snowboard boot. When this type of snowboard boot is used, the ankle can swivel or tilt in unison with the snowboard boot in the lateral direction with respect to the rider.
When the snowboard boots are affixed to the snowboard, the left foot is usually positioned to be the controlling foot. The longitudinal line of the left snowboard boot is usually inclined towards the direction of travel (i.e., towards the left side) with respect to the major axis of the snowboard (the direction of forward progress). This angle of incline is usually about 27xc2x0. The main reason for this particular angle of incline is that it facilitates vision in the direction of travel.
In order to make the snowboard go forward in the direction of its major axis, the tilt or swivel of the left foot should be directed in the direction of travel. In known swivel designs, the direction of tilt is inclined with respect to the direction of travel. That is, in known swivel designs, the direction of tilt is inclined by 27xc2x0 with respect to the direction of travel. These known swivel and tilt designs result in a loss of the propulsive force which propels the snowboard in the direction of travel.
Furthermore, the human ankle is known to have a three-dimensional arch structure that can easily tilt to the left or right when the leg is inclined forward, whereas tilting to the left or right is more difficult when the leg is not inclined. This three-dimensional arch structure thus makes it difficult to bend the foot in the lateral direction when in an erect posture. Swivel and tilt designs must therefore take into account this three-dimensional arch structure, as well as the angle of diagonal attachment of the snowboard boot to the snowboard. Swivel and tilt designs must also be reexamined in connection with piping competition, in which strong propulsive force in the direction of travel is required.
The present invention is directed to a snowboard boot which allows the rider to apply maximum propulsive force to the snowboard without interfering with the natural movement of the ankle. In one embodiment of the present invention, a snowboard boot includes a heel member and a leg member positioned above the heel member. The heel member and the leg member are secured to the boot so that the leg member is capable of movement relative to the heel member about an axis of rotation that is vertically inclined no more than xc2x145xc2x0 and that lies within a plane that is inclined relative to a longitudinal plane which divides left and right sections of the boot.
In other words, a snowboard boot which has general lateral symmetry is designed to pivot around an axis which intersects the plane of symmetry. As noted above, tilting motion of the ankle in the lateral direction is facilitated when it is accompanied by tilting motion in the longitudinal direction. Due to the aforementioned three-dimensional structure of the ankle, pivoting motion in a pivoting plane which is inclined with respect to the vertical plane in which the axis of the anklebone lies is easier than pivoting motion in the vertical plane in which the axis of the anklebone lies. Thus, the tilting design which pertains to the present invention is consistent with the three-dimensional arch structure of the ankle.
When the snowboard boot is attached such that it is inclined diagonally with respect to the major axis of the snowboard, i.e., to the direction of travel, pivoting motion of the foot in the diagonal direction provides propulsive force in the direction of travel to the snowboard boot. Since the rotational force (the component force which acts so as to rotate the snowboard) is zero or very small in this case, the loss in propulsive force produced by the foot acting on the snowboard is minimized, and this propulsive force therefore has high propulsive efficiency. This high propulsive efficiency is useful in piping competitions.